The Jargon File (version 4.4.7, 29 Dec 2003):

Indent-o-Meter


    [] A fiendishly clever ASCII display hack that became a brief fad in
    1993-1994; it used combinations of tabs and spaces to produce an analog
    indicator of the amount of indentation an included portion of a reply had
    undergone. The full story is at http://world.std.com/~mmcirvin/indent.html.